ACDelco GM Original Equipment Engine Coolant Crossover Pipe Gaskets are used to seal the interface between the coolant crossover pipe and the cylinder heads, engine block, or another engine component. The gasket may be made of fiber or a rubberized composite material that provides a liquid-tight connection. The gasket keeps the engine coolant in and keeps air out. These original equipment gaskets have been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.